1. Field of the Invention
The present invention relates to a gas burner system and more particularly to a gas burner having a flame re-ignition system wherein a plurality of spark type ignitors are provided.
2. Description of the Related Art
Cooktop burners are typically ignited by the user opening a rotary valve in the fuel supply line to provide a flow of the fuel gas to the burner whereupon a set of switch contact are simultaneously closed for electrically energizing an ignitor having an electrode disposed to provide a spark in the stream of fuel/air mixture emanating from a port in the burner. When the spark gap of the electrode is bridged by flame, the resistance of the gap is effectively lowered, enabling current to flow across the gap. Accordingly, current flow across the spark gap, enabled by the presence of a flame creating a conduction path across the spark gap, may be electrically detected as an indication or proof of the presence of flame by a flame sensing circuit connected to the ignitor. This phenomena has been widely employed for combining the function of an ignitor with that of a flame sensor by providing flame sensing electrical circuitry which, upon the loss of flame, electrically detects the change of a current in the electrode and reenergizes the ignitor automatically.
One shortcoming of these prior art flame sensing systems is that if transient air currents extinguish the flame about only a portion of the annular periphery of the burner which includes the flame sensor, the fame sensor can not determine whether the flame has been totally extinguished and an annoying reenergization of the ignitor occurs. This is sometimes referred to as nuisance sparking wherein re-ignition sparking occurs even though a flame exists about a portion of the burner.
Prior efforts to avoid this nuisance sparking have focused on ways or means of preventing flame loss in the region of the flame sensing ignitor. U.S. Pat. No. 5,492,469 discloses a burner having a pocket formed in the periphery of the burner for receiving an ignitor. The pocket provides a protected region for maintaining flame about the ignitor.